In common with most of western Bc, Abbotsford has an Oceanic Climate (Köppen Climate Classification Cfb) typical of coastal mid-latitudes, with the distinction of having warm and dry (albeit short) summers more in common with a Mediterranean (Csb) climate. The area falls under USDA Hardiness Zone 7b (an average annual minimum temperature between -12.2°C and -15°C) and AHS Heat Zone 2 with an average of 7.3 summer days at or above 30°C. Abbotsford's proximity to the Pacific Ocean provides milder winters and much greater precipitation than areas east of the coastal mountains. The influence of the Pacific limits the length of winter -- spring-like conditions may occur as early as mid-February -- and delays the onset of summer, with cloudy and showery weather often persisting until the second week of July. Conversely, the descent into autumn and winter is comparatively abrupt compared to other areas of the country.
Spring is initially cool and generally showery before gradually warming and drying in June. Below freezing temperatures may occur overnight into May, and snow has been known to fall until the end of April, but it rarely accumulates to more than a few centimeters and generally melts the same day. Normal daytime highs range from near 10°C in March to the low 20's in June. During exceptionally warm periods, the temperature can reach into the mid 20's during March and April, and can exceed 30°C from May onwards.
Summer in southwestern BC is known for its relative dryness. During July and August, it is not uncommon for the area to receive little or no rainfall for two consecutive weeks or longer. August averages only 20% of November's rainfall, and only about 16% of annual precipation falls between June 1st and October 1st. Un-watered grass often turns brown in July and may not need to be cut until September, when significant rains become more likely.
Rain that falls during summertime is normally quite light, but can occasionally come in the form of thunderstorms, of which about eight occur annually. Thunderstorms typically signal the end of a period of hot weather and a return to cooler, cloudier conditions.
Due to its inland location, Abbotsford's summers are relatively warm compared to areas near the Strait of Georgia. The average daily high in August is 23.8°C, but highs over 30°C are not uncommon in most years. The temperature can be expected to reach or exceed 30°C on an average of 7.3 days per year, mainly in July and August. The highest temperature ever recorded was 38.0°C on July 29th, 2009.
Relative humidity levels tend to be moderate, averaging near 40% during the warmest time of the day. As a consequence, nights are usually fairly comfortable, even during periods of hot weather. It is rare for the temperature to stay above 20°C at night, often falling as low as 10°C. Large duirnal ranges in temperature are common under clear conditions, and during warm spells, the temperature may range by 20°C or more in a 12 period (eg. a morning low of 10°C and an afternoon high of 30°C).
Autumn is characterized by increasingly unsettled and cooler conditions. Temperatures may still reach the mid or even upper 20's C at first, but rainfall becomes more frequent and temperatures drop in October. Frost may occur in late September, and at any time during October.
October 1st heralds the unofficial start of the rainy season, but the heaviest rains occur in November, which averages 234.3 mm of rain and 6.3 cm of snow (240.9 mm combined). According to Environment Canada, Abbotsford is the fourth wettest of 100 major cities in Canada, with 1573.2 mm of combined rain and snow annually. A weather pattern known as the Pineapple Express often brings significant rainstorms in autumn and winter.
The earliest snowfall has been known to occur at the end of October, but more frequently occurs in November. During milder years, there may be no snow until after the winter solstice. Occasionally, there will be a spell of sub-freezing weather in late November or early December; this may be accompanied by snow and high winds, but is usually short-lived.
With a mean temperature of 2.5°C in January, Abbotsford's winters are cool, but relatively mild compared to most of Canada. However, the consistently overcast and damp conditions may be subjectively less pleasant than colder, sunnier weather.
The coldest month on record at Abbotsford International Airport is January 1950, with a mean temperature of -8.6°C (an average high of -4.7°C and an average low of -12.4°C). It was during this time that Abbotsford also set its all-time record low temperature of -21.1°C, on the 18th of that month.
Snow occurs frequently in the surrounding mountains, but much less often near sea level. Although snowfall is sporadic, there is a general misconception by visitors and residents in other parts of the country that the area does not receive any snow at all, but the truth is that Abbotsford averages 63.5 cm of snow per year, and there has never been a winter when snow has not been observed at both Abbotsford International Airport and Vancouver International Airport. As a matter of fact, Environment Canada currently ranks Abbotsford 44th and Vancouver 59th under the category "Most huge snowfall days (25 cm or more)" out of 100 major Canadian cities, placing them above cities such as Calgary (74th place) and Toronto (99th place). Years or even months with snowfall surpassing the 100 cm mark are also not completely exceptional; the former occurred twice in the 1990s, while January of 1954 saw more than 140 cm of snow.
Snow that falls tends to be quite wet, which when combined with typical winter temperatures rising above and falling below freezing throughout the course of the day, can make for unusually slippery road conditions.
Snowfall accumulations tend to vary greatly by year and season. During the winter of 1990-1991, 152.3 cm fell; the next winter, only a trace of snow was recorded. In the year 1996, 199.2 cm (over six feet) was recorded; the next year, only 6.2 cm fell. Serious snow storms occurred most recently in December of 2008, when as much as 60 cm fell in the days leading up to Christmas. Abbotsford can expect a White Christmas once every five years on average.
Snowfall Records for Abbotsford International Airport
• Snowiest Year: 213.3 cm (1971)
• Snowiest Month: 140 cm (January 1954)*
• Extreme Daily Snowfall: 49.8 cm (January 21st, 1954)
• Highest Snow Depth: 69 cm (December 30th, 1996)
*In comparison, Toronto's snowiest January was 118.4 cm in 1999.
Recent Unusual Weather• In January 2012, an arctic air mass caused temperatures to drop to levels not seen since the mid 1990's. The maximum temperature on January 18th only climbed to -9.0°C, the coldest daytime high of any day since Dec 28th, 1996. The same day, the minimum temperature fell to -14.8°C, the coldest minimum temperature of any day since Jan 7th, 1993. Wind chill temperatures fell as low as -24°C during the morning hours. Apart from these extremes, the cold snap was otherwise unremarkable, short-lived, and snowfall was moderate compared to other notable events such as the December 2008 cold snap.
• In the final week of July 2009, a record-breaking heat wave settled into the region. The heat wave was preceded by heavy thunderstorms, which left the air thick with moisture. As temperatures increased, humidex values soared into the mid 40's. The resulting scramble for air conditioning units left many retailers out of stock. On Wednesday, July 29th, the temperature peaked at 38.0°C, breaking the all-time heat record of 37.9°C which had been established just two years earlier on July 11th, 2007. The hot temperatures were forecast to continue through Friday before cooling to near 30°C over the weekend.
• During the second half of December 2008 and the first 10 days of January 2009, unusual amounts of snow were recorded, combined with a prolonged period of colder-than-average temperatures. By Christmas Day, well over 50 cm of snow had accumulated, much of it falling on Christmas Eve and early Christmas morning. Many people were forced to cancel Christmas plans, as some roads had become impassible.
• In November 2006, Abbotsford experienced abnormal levels of rainfall, snowfall, and wind. By the end of the month, 421.8 mm of precipitation had been recorded, and severe windstorms had damaged homes and infrastructure, causing power outages. To make matters worse, 53.5 cm of snow was recorded from the night of November 25th to the morning of November 27th. After the snow storm, the temperature dropped to -11.6°C on November 29th.